1. Field of the Invention
The present invention relates generally to methods for controlling the electrochemical surface potential on a surface and use thereof. In particular, the present invention relates to method for the two-dimensional spatially varying control of the electrical surface potential on the surface of a conducting substrate and method using such control for discovering a target, detecting a target, and systems for implementing such method. The present invention is useful, e.g., for combinatorial catalyst discovery, chemical sensing and biochemical sensing.
2. Technical Background
Electrochemistry is a branch of chemistry that deals, in part, with processes occurring on surfaces (i.e., electrodes) due to interplay between electrical and chemical effects. This field encompasses a variety of phenomena and applications of technological importance including electrocatalysis, corrosion, batteries, fuel cells, double-layer capacitors, electrochemical sensors, electrochemical synthesis, electroplating, electrophoresis, electrochromic displays, etc. In many of these applications, surface processes can be manipulated by controlling the potential or the current of one or more electrodes in the system.
In conventional electrochemical experiments, uniform surface potentials are applied to electrode surfaces. Although there can be non-uniformities in surface potentials due to the electronic resistance of the electrodes, the intent is typically to apply a uniform electrochemical potential across the electrode surface so as to ensure that each and every point on the electrode surface has the same surface energy. Such uniformity can lead to reproducible electrochemical processes across the electrode surface. With the advent of combinatorial materials and methods, such as, for example, drug discovery, conventional approaches to scientific problems have changed to allow greater throughput of experimental samples and faster cycle time for the development of new products. Researchers across a wide variety of fields such as drug discovery, materials research, homogeneous and heterogeneous catalysis, surface chemistry, have adopted combinatorial methods due, in large part, to the ability of combinatorial methods to systematically study the performance of materials as a function of a relevant material or processing parameter in an accelerated fashion. For example, combinatorial methods have enabled catalyst discovery processes to be shortened from several decades to a few days or less. Combinatorial processes typically require both a method to create a spatially varying library of materials and analytical methodologies to screen and map the performance of each library component.
Thus, the ability to control the surface energy of a particular library material (e.g., a substrate) as a function of position can be determinative to the successful outcome of a combinatorial experiment. Such control can be in an array platform or a gradient platform. In an array platform, the surface energy across a surface is controlled by adjusting individual points, whereas in the gradient platform a gradual change in surface energy is achieved by controlling a few specific points. There are several ways one can envision control of surface energy of a particular material, including the control of temperature, local composition of precursor materials, pressure, etc.
Thus, a need exists for improved control of surface energies for combinatorial processes, such as, for example, the creation and control of surface energy gradients across the surface of an electrode. The present invention provides various methods for creating and controlling such a gradient.